The present invention relates to a radio frequency perforation guidewire as well as a radio frequency generator. The invention is able to allow surgeons and cardiologists to treat pediatric patients that require a transcatheter perforation to deal with congenital heart malfunction. More particularly, the invention is directed to a perforation guidewire which can be energized by radio frequency current to first create, and then enlarge, in a controlled manner, a hole in the atrial septum or any other heart tissue to improve intertribal communication. The invention is applicable to any tissue in the body where it would provide positive results.
RF guidewires and catheters for surgical perforation are known in the art. The terms, xe2x80x9cguidewirexe2x80x9d and xe2x80x9ccatheterxe2x80x9d, as used herein, mean substantially the same thing, more explicitly the term catheter means: a tubular medical device for insertion into canals, vessels, passageways, or body cavities, to allow a guidewire passage through, or to deliver or remove fluids, or to permit energy to travel through, or to permit a balloon or any other catheter to be passed over or through it. And the term guidewire means: a wire like medical device that is used to deliver energy to required areas, or used to guide other medical devices, either over or through it.
EP 0 315 730 A3 to Osypka et al. describes a device to dilate and/or open up using heat blood vessels which are morbidly contracted or clogged. U.S. Pat. No. 5,364,393 to Auth et al. describes a guidewire to traverse an occlusion in an arterial lumen to allow subsequent passage of a therapeutic device for treatment.
Newborn pediatric patients who have severe cyanotic problems; patients with pulmonary valve atresia and intact ventricular septum present a formidable therapeutic challenge to pediatric interventional cardiologists. High mortality rates are associated with this congenital heart defect despite numerous advances in the field.
The most common surgical approach consists of creating a systemic to pulmonary artery shunt together with an open pulmonary valvotomy. The final step which is conditional on the right ventricle developing sufficiently is the closure of the atrial septal defect and the systemic to pulmonary shunt.
Alternatively, the feasibility of percutaneous transcatheter xe2x80x9chot tipxe2x80x9d laser-assisted balloon dilation has been shown. Several drawbacks exist with the laser system including the necessity of excessive initial capital outlay, risk to staff of retinal damage, and inconvenience of transporting a cumbersome system between laboratories and/or hospitals.
The presence of free electrons and ions in solution within the tissue structure permit the flow of electrical currents. Body tissue has an electrical resistance, and consequently, passage of electrical currents through the body dissipates some energy in the form of heat. At high enough current density levels, vaporization of the entrained tissue water occurs. If the speed of the vaporization process is sufficient to prevent diffusion through tissue, the said tissue will rupture and incise. The aim of electrosurgery is to produce linearly such ruptures.
An electric current can irritate nerve and muscle cells triggering specific reactions such as muscle contractions and sensations of pain. The intensity of the reactions depends on the intensity and frequency of the current used. At frequencies above 100 kilohertz, the muscle fibers are unable to respond.
Electrosurgery is accomplished by passing RF current through a small electrode (the active electrode) in the form of a scalpel or needle into tissue, and completing the electrical circuit through the tissue by attaching a large electrode plate (the indifferent electrode) elsewhere on the body.
It is an object of the present invention to provide an RF perforation guidewire to first create, and then enlarge in a controlled manner, a hole in the atrial septum or any other heart or body tissue to improve intertribal communication.
It is an object of the invention to create new passageways in the tissue.
It is also an object of this invention to traverse through newly created channels in the tissue.
According to one aspect of the invention, there is provided an electrically conductive guidewire for creating a hole in body tissue to be perforated and then enlarging the hole, comprising: a guidewire body with a substantially continuous diameter having a proximal end and a distal end, a distal tip portion including an electrically conductive exposed tip for creating a perforation when RF current is applied and for preventing the creation of a perforation when RF current is not applied, an insulated electrical conductor means for passing electric current from the proximal end to the tip, and a dilator region between the distal end of the guidewire body and the distal tip portion for expanding the hole, and having a tapered profile.
According to another aspect of the invention, there is provided an electrically conductive guidewire for creating a hole in body tissue to be perforated and then enlarging the hole, comprising a guidewire body with a substantially continuous diameter having a proximal end and a distal end, a distal tip portion connected to the distal end of the guidewire body including an electrically conductive exposed tip for creating a perforation when RF current is applied and for preventing the creation of a perforation when RF current is not applied, an insulated electrical conductor means for passing electric current from the proximal end to the tip, an inflatable balloon located circumferentially on the guidewire body for expanding the hole, and a catheter located on the guidewire body and in communication with the balloon for delivery of fluid to the balloon for its inflation.
According to a further aspect of the invention, there is provided an RF signal generator for a surgical RF perforation instrument including an RF voltage source connected to the instrument, an RF impedance measurement circuit for measuring a level of impedance of tissue contacted by the instrument, and control means for monitoring the RF impedance measurement and generating a shut-down control signal when a change in the impedance measured indicates that the instrument has perforated the tissue.